This invention relates to game balls, and, more particularly, to an inflatable game ball having a synthetic leather cover which includes a polyurethane coating which is capable of absorbing sweat.
Game balls such as basketballs, soccer balls, and footballs conventionally include an inflatable bladder and a cover. The bladder may be reinforced with windings of nylon thread, polyester thread, etc. The cover is conventionally formed from panels of leather, synthetic leather, rubber, etc.
Synthetic leather covers have been well received as a substitute for more expensive leather covers. Synthetic covers are soft and easy to grip when dry. However, a synthetic leather cover becomes difficult to grip when the cover is wet with sweat. A genuine leather cover, particularly after breaking in, has small holes which absorb sweat so that the ball retains its grippability. On the other hand, a synthetic leather cover commonly includes a polyurethane coating which is relatively impervious to sweat.
Synthetic leather materials for basketballs and other game balls are available from Kuraray Co., Ltd. and Teijin Cordley Ltd., both of Japan. Basketballs using the Kuraray material are sold in the United States by Spalding under the name ZK 1000 Composite. Basketballs using the Teijin material are sold in the United States by Wilson under the names Jet Evolution and MP 5000.
The Kuraray material is described in Japanese Patent Publication Nos. 60-17871, 62-44074, 63-5518, and 64-20866. As described in those publications, a mat of fibers is formed from small denier or small diameter fibers which are made from two different polymers, e.g., polyethylene and nylon. The mat is impregnated with a solution of polyurethane in dimethyl formamide (DMF) solvent. The polyurethane-impregnated mat is wet-coagulated in a bath of water and DMF. The resulting product is immersed in toluene to extract out the polyethylene, leaving the nylon fibers in a so-called "islands-in-the-sea" base fabric. The base fabric is then coated with polyurethane dissolved in a first solvent and substantially coated with polyurethane dissolved in a different solvent. The resulting synthetic leather is cut into panels and applied as cover material to basketballs and other game balls.
U.S. Pat. Nos. 5,310,178 and 5,669,938 describe the use of synthetic leather of the type described in the Kuraray publications as a cover material for basketballs.
The polyurethane coating of the foregoing synthetic leather is substantially impervious to sweat. As a result, many players prefer to use basketballs which are covered with genuine leather.